Motorcycle sound simulator for non-motorized vehicle

ABSTRACT

A motorcycle sound simulator for non-motorized vehicles is disclosed having a sensor (16) to detect motion of a wheel (18) and transmit electrical signals to a control unit (12). The control unit, through its microprocessor, produces a firing period (520) which includes a pulse train burst (522) and silence (524) which are respectively altered in length to produce motorcycle-like sounds. Other motorcycle attributes such as shifting gears (514), acceleration (508), deceleration (512), misfire (516), and failure to start (504) are provided and audio output is generated with audible tones corresponding to a motorcycle-type sound.

TECHNICAL FIELD

The present invention relates to a device for generating realisticsounds of motorcycles and using such sound generators on other vehicles,typically non-motorized types, such as a bicycle.

BACKGROUND OF THE INVENTION

The popularity of off-the-road motorcycles known by their colloquialname "dirt bikes" has been growing steadily over the years and the soundof such motorcycles is easily identifiable by its "revving" sound.

More recently, bicycle manufacturers have been designing their smallerbicycles to have many of the appearance characteristics of suchmotorcycles, namely heavy duty wheels, knobby tires, strutted highrisehandle bars, handle grips, and a sturdy low frame. There is in factalready a hobby of racing such bicycles on the same terrain as would beused for off-street motorcycles. To enhance the realism of these specialbicycles, it would be desirable to simulate the sounds created by themotorized version thereof without actually adding motors to the bikeswhich would destroy their usefulness as safe toys.

It would be desirable to have this simulation realistically parallel thechanges in acceleration and deceleration of the bicycle during its rideon an uneven track as well as some of the other characteristics ofinternal combustion engines, including misfire and failure to start.

The present invention provides such a simulator which is capable ofmonitoring the acceleration and velocity characteristics of the bicycleand producing appropriate sounds in response thereto.

SUMMARY OF THE INVENTION

The present invention is related to a motorcycle sound simulator for usein non-motorized vehicles having a sensor attached to the vehicle todetect and measure the rotation of a wheel and to generate an electricalsignal therefrom, means capable of determining the relative velocity ofthe vehicle from the signal, means capable of determining the relativeacceleration of the vehicle, and means for producing an audio output inresponse to the velocity in an acceleration, the output having audiocharacteristics corresponding to the sounds created by a motorcycle atlike velocities and accelerations.

In accordance to further aspects of the invention, means are providedfor step-wise continuous changes in the audio frequency, the changesoccurring at particular velocities and accelerations producing audiocharacteristics corresponding to shifting of gears on a motorcycle.

A further aspect of the invention includes a starting sequence whichrandomly determines whether the attempted start of the simulator willproduce a start sound or a failure to start sound.

According to a further aspect of the invention, means are provided toproduce an intermittent audio output corresponding to a misfire of themotorcycle and the misfire being randomly generated with a probabilitywhich increases as the audio frequency increases.

According to a further aspect of the invention, the simulator includes asilent period of random length being inserted between the periodic soundgenerated to eliminate natural resonant sound caused by the periodicnature of the audio output, thereby leading to a cleaner and morerealistic sound.

Various advantages and features of novelty which characterize theinvention are pointed out with particularity in the claims annexedhereto and forming a part hereof. However, for a better understanding ofthe invention, its advantages, and objects attained by its use,reference should be made to the drawings which form a further parthereof and to the accompanying descriptive matter, in which areillustrated and described certain perferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings wherein like numerals refer to like elements throughoutthe several views:

FIG. 1 is a side plan view of a bicycle having the preferred embodimenton the invention attached thereto;

FIG. 2 is a schematic drawing of the logic circuitry of the preferredembodiment;

FIG. 3 is a representative flow chart of major functions of thepreferred embodiment;

FIG. 4 is a representative trace of the audio output at idle;

FIG. 5 is a representative trace of the audio output at high speed;

FIG. 6 is a representative trace of the audio output at misfire,

FIGS. 7-26 are block diagrams which illustrate the function of thepreferred embodiment;

FIG. 27 is a representative trace of wheel speed versus vehiclevelocity; and

FIG. 28 is an object code for the preferred embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, there is a bicycle 10 shown having mounted thereonan electronic control unit 12 attached by brackets 14 to the frame ofbicycle 10, and a rotary sensor 16 also attached to the frame and whichengages either the rubber sidewall of the rear wheel 18 or the rimthereof. Sensor 16 is, in the preferred embodiment, constructed similarto a permanent magnet generator known in the bicycle art for poweringhead and tail lights. Thus, sensor 16 includes a rotating portion 20 anda fixed portion 22 attached to the frame. The rotation of portion 20generates an electrical signal or, alternatively, a variable resistanceor a Hall-effect switch could be used to transmit interrupts (ratherthan generating a current) to the control 12 for interpretation by theelectronics therein.

Turning to FIG. 2, namely the schematic diagram, there can be seen theessential features of the electronic circuitry within unit 12. At theheart of the system is a microprocessor 30 which, in the preferredembodiment, is an Intel 8048. The data input pins DB-0 to DB-7 are usedonly at initialization and it can be seen that the sample time frame of192 units (of 350 microseconds each) is hardwired thereon. This value isthe number of timer interrupts in the wheel sensor sample, as will beexplained hereinafter. Pins P20-P27 are supplementary data inputs andare not presently used in the preferred embodiment.

Pins P10-P17 provide the audio output pulse train. In this embodiment,only P17 is used, however it will be appreciated by persons skilled inthe art that different sounds and different amplitude levels can beobtained by using one or more of the other output pins. The wheel sensor16 is indicated only in its fixed coil 32 and would be preferablycharacterized as a 12 pole permanent magnet generator which produces asinewave whose frequency is proportional to the wheel rotation speed.Diode 34 eliminates the negative going pulses from the sinewave outputand capacitor 36 provides a noise filter. Transistor 38, along withresistors 40 and 42, provide simple amplification and their output isfed into nand gates 44, 46 and 48 to produce a short pulse ofapproximately 10 microsecond output which in turn is input to the INT(interrupt) input of the microprocessor 30. The system is powered by adry cell battery source 50 of six volts and is controlled by an On/Offswitch 52. The actual "start" switch 54 must also be operated toinitiate the audio sequence.

A capacitor 56 is applied across the reset and External Access (EA) andtied to ground inputs.

The clock inputs 1 and 2 have an L-C network applied across themincluding an inductor 58 and capacitors 60 and 62 which provide a clockfrequency of approximately 5 megahertz.

At the output end of the circuit, output line P-17 is connected to aresistor network of resistors 64 and 66 which control the amplitude attheir intersection point to be approximately 3.3 volts when P17 is atlogic 0. When P17 is at logic 1, the junction will be pulled up to theVCC. The signal is then fed into a operational audio amplifier 70 whichis configured as a non-inverting type with the speaker load connectedbetween the output and VCC. Therefore, when the input is high the outputwill be high and visa-versa. Resistor 72 provides the gain of theamplifier preferably set at about 3 and capacitor 74 provides lowfrequency roll-off. Frequency compensation is provided by resistor 76and capacitor 78 while capacitor 80 provides decoupling.

With the circuit shown in FIG. 2 in place, the sounds produced arecontrolled by a series of instructions programmed into themicroprocessor. These instructions are provided in the form offlow-charts, which form the remaining drawings of this disclosure andshould be understood by a person skilled in this art.

FIG. 3 of the drawing provides an overall conceptual understanding ofthe major aspects of the preferred embodiment of the present invention.After turning on the power, the operator will then depress the startswitch thereby attempting to start the system (block 500). One of thefeatures of the system is that by random generation, some of theintended starts will not produce an "ignition"(block 502) but rather ano start condition (block 504) which results in an increasing audiofrequency followed by a decreasing to zero. If the start is successful,the system goes to an idle condition (block 506) which maintains aminimum audio frequency output. From there, motion of the wheelcontaining the sensor will produce an accelerating frequency (block 508)to a possible cruising frequency (block 510) from which there may bedeceleration (block 512) or a gear change (block 514) which would causea step-wise increase or decrease in audio frequency depending on whetherit is a "upshift" or "downshift". In any of these conditions, a"misfire" may be produced (block 516) which results in an audio outputcharacterized by an audio output of the type shown in FIG. 6 andcorresponding to a misfire sound characteristic of a motorcycle.

By means of an interrupt in the microprocessor, the audio output isgenerated (block 518) which is related to the velocity and misfire datacreated as explained above.

The audio output is more fully explained in FIGS. 4-6. To create a soundcharacteristic of a motorcycle, we have chosen to create a unit ofmeasure called the firing period (block 520) which includes a pulsetrain burst (block 522) and a period of silence (block 524). The firingperiod 520 is repeated so long as the system is running. As illustratedon FIG. 4, a series of positive going pulses of varying widths aregenerated during the burst portion (block 522) and have an overallperiod of 40 units, each unit corresponding to 350 microseconds and thesilent period being 75 units. The overall firing period therefore is 115units.

As will be explained hereinafter in the appropriate flow chart, tochange the frequency of the sound in response to increasing velocity ofthe vehicle, the firing period (block 520) is shortened but it is onlythe silent period (block 524) which is actually reduced leading to atrace such as shown in FIG. 5 wherein the second pulse train burst(block 526) follows the end of burst 525 with no silent period. This iseffectively the highest speed output generated by the system. "Gearshifting" is provided to keep all realistic velocities usable by thesystem.

To add realism to the system, a "misfire" sound is generated at randomintervals. This misfire sound is created by truncating the pulse trainas shown in FIG. 6 where the misfire burst (block 527) is much shorterthan the normal burst (block 529) as the silent period is much longer.The probability of a misfire depends on the frequency of the output atthat time. A lower speed (i.e., longer firing period) will result inmore misfires. At the beginning of each firing period, a random numberis generated and masked with a number from a look-up table. The resultof an AND operation with the mask produces a result which, if zero,results in a misfire. By substituting different masks, the probabilityof a misfire at higher speed is reduced.

Turning now to the flow charts wherein the operation of the system isexplained in detail, FIG. 7 illustrates the initialization routine.First all input and output ports are initiated (block 110). Thereafter,the program variables are initialized (block 112), timer interrupts areenabled (block 114) and the system proceeds to generate sounds with thestarts up routine (block 116). All of this begins after switches 54 and52 have been closed.

Bridging FIGS. 7 and 8 is the connecting block 118. The main sub-routineshown on FIG. 8 begins by calculating the firing period based on thevehicle wheel speed and present "gear" number. The gear number is also afunction of wheel speed. To determine the gear number, it is firstnecessary to find a running average of pulses from the sensor. A runningaverage is used to smooth out abrupt changes. According to theflow-chart, first the number of pulses coming from the wheel sensor arecounted during a fixed interval of 192 units (350 microseconds eachalthough at start a period of 450 microseconds can be used to create alower tone) (block 120). Then, the count is stored in a 14 byte circularbuffer (block 122) to maintain the running average. The buffer entriesare summed (block 124) and the difference between the previous sum andthe new sum indicates the rate of change in the wheel speed (block 126)and therefore the rate of acceleration or deceleration.

Block 128 carries over the flow-chart from FIG. 8 to FIG. 9. Adetermination of whether the acceleration is positive or negative ismade (block 130). If negative, the sub-routine designated by number 132is followed (explained hereinafter). If positive, a determination ismade whether the differential is greater than a predetermined maximumacceleration allowed (block 134). If so, the sum is reduced to themaximum acceleration allowable (block 136). If not, block 136 isskipped. The purpose for limiting the rate of acceleration is to preventan unrealistic "racing" sound which would be produced. Block 138provides transition in the flow-chart to FIG. 10.

FIG. 10 illustrates the entry point for block 132 (decelerationcircumstance). Looking to FIG. 10, in the event that the change inacceleration was negative (block 132) a determination is made as towhether this deceleration was beyond the maximum predetermined value(block 140). If so, this deceleration is reduced to the predeterminedvalue (block 142). Then the new sum replaces the old sum in memory(block 144). Block 146 provides the transition to the next flow-chartshown in FIG. 11.

In the flow-chart shown in FIG. 11, a calculation is made of the firingperiod which is mathematically determined by multiplying a minimum valueof 18 time units times a scale factor and the number of entries in thebuffer (=14) (block 150) divided by the sum of entries in the buffer(block 150).

The scale factor is found from a look-up table from preprogrammed tables(block 148) and is essentially the "gear ratio". Their numerical valuesare chosen according to the desired audio frequency at any particularvehicle velocity.

If there is an overflow as a result of division (block 154), a defaultvalue is selected as the longest allowable firing period whichcorresponds to the "idle" speed. Without the default, the sound wouldstop, giving the effect that the motor had "died". Block 165 providesthe transition to FIG. 12 of the drawings.

If the result of the division produces a period which is less thanpredetermined points of shifting to a higher gear (block 158), the gearnumber or scale factor is incremented (block 160). In such case, theprogram then reverts back to the sub-routine indicated by block 146.Otherwise, a test is made to determine if the period length is greaterthan the present downshift point (block 162). If it is, the gear numberis decremented (block 164) and the program proceeds to sub-routineindicated by block 166.

If the period is not greater than the downshift point, the programproceeds to sub-routine indicated by block 168. FIG. 13 starts withblock 166 and begins by testing to determine if the gear number is zero(block 170). If it is, it is replaced by the default value of 1 (firstgear) with the longest period available. Thus, the speaker will beproducing an idle sound (block 172). If the gear number was not equal tozero, the program proceeds to the sub-routine shown in FIG. 7 beginningwith block 146.

With the gear number set to 1 or an entry into the system through block168 in FIG. 12 (which is a period not requiring downshift), this periodis stored in memory awaiting the next pulse from the timer interruptroutine (block 174).

To create additional realism, a "misfire" sound is generatedoccasionally. This is accomplished by fetching a mask byte from alook-up table . The mask is used to determine if the current firingperiod is a misfire. The mask value depends on the length of the firingperiod and the probability of a misfire decreases as the perioddecreases (that is, engine speed increases) (block 176). The misfirecondition is calculated as follows. A 16-bit number is generated by arandom number generator of which the lower eight bits are used. Eightbits are masked by a number in a look-up table which includes some zerobits, and it is the number of zero bits which actually determine theprobability for misfire. A misfire is ordered if the masked bytecombined by an AND operation with the random number produces a zeroresult. At higher speeds, the mask has fewer zero bits and at lowerspeeds it has more. In the lowest speed, the mask byte has six zero bitsand two non-zero bits making the probability of a misfire one in four.If a misfire is ordered, the firing period is altered as shown in FIG. 6so that the misfire burst has nine time units (of 350 microseconds) andthe remainder is silent. (This paragraph should be moved down to theposition where FIG. 22 is located). The sub-routine continues on FIG. 10from block 178.

A test is then made to determine if the last two speed samples were lessthan the minimum (block 180). If they are, the assumption is made thatthe bicycle has stopped and that the system should go to idle. This isto prevent an unrealistic sound of rapid downshifting in a "skid"situation. The gear number is then changed to 1 and the longest period(default) is substituted in memory (block 182) and the program revertsto its starting point 118 in the main sub-routine. If the speed was notless than the minimum for the last two samples, a determination is madewhether the present period is greater than the initial downshift pointestablished earlier (block 184). If not, the program proceeds to thesub-routine indicated by numeral 186, otherwise the upshift anddownshift are returned to their initial positions (block 188) and theprogram proceeds back to the beginning sub-routine 118 in FIG. 4.

The shift set-points are now adjusted according to the rate ofacceleration or deceleration. A high rate of acceleration will cause theshifting points to occur at higher speeds (i.e., shift up later). A highrate of deceleration will cause the shift point to occur at lowerspeeds. Skipping to FIG. 27, there can be seen a schematic trace of arepresentative engine speed versus vehicle speed in relative terms. Onthe velocity scale, shift points a, b, c and d are shown. Points a and band all space therebetween correspond to the shift from first to secondgear and it can be understood that the shift point will move from pointa toward point b as the frequency (engine speed) increases as shown onthe vertical scale. It is also worth noting that the minimum frequencywhich occurs right after a shift is greater at every succeeding gear asone would expect in operating a motorcycle to avoid the condition knownas "lugging". A test is therefore made to determine whether the activityis acceleration or deceleration (block 190). If deceleration, theprogram proceeds to sub-routine indicated by block 192. Foracceleration, the rate (namely the change in velocity) is divided by ascaling factor 6 (block 194) and the truncated result (no fractions) issubtracted from the current shift point, in effect reducing the firingperiod. The result is that shifting will occur at a higher engine speed(block 196). If the result of this decrease in shift point is less thanthe minimum shift point (block 198), the shift point is set to itspredetermined minimum (=18 units) (block 200) and the program returns toblock 118 in FIG. 8 in either case. (This is FIG. 15).

In FIG. 16, deceleration, as detected by the result of block 192, isconsidered. The rate of deceleration is scaled by a factor 6 and theresult is decremented from the current shift point (block 202). Theresult is further decremented by one and truncated so that thedeceleration will have less effect on moving shift points thanequivalent acceleration.

The new shift points are then determined by addition of this truncatedvalue (block 204). If the result of the addition is greater than theinitial value (block 206), then the shift point is set at the minimum(i.e., their initial values) (block 207), then return to sub-routine 118in either case.

FIG. 17 illustrates the sub-routine which enables the sensor interruptsand decrements the sample interval counter during which the wheel sensorpulses are enabled and counted. First, a "time out" counter is set to aninitial value and the sensor pulse counter is set to zero (block 208).After the initial value is set in the counter, a determination is madeto see if the sensor 16 has stopped (block 210). If it has, either thewheel is stopped or the sensor is broken. If no sensor pulse isreceived, the time out counter is decremented (block 212) and adetermination is made if the time out counter equals zero (block 214).If it does equal zero, the program exits to block 216 and returns asensor pulse count of zero indicating that no sensor pulses werereceived during the time out period. If a pulse has been received asindicated by block 210, the program exits to a sub-routine indicated byblock 218.

FIG. 18 illustrates the sub-routine beginning with block 218 wherein theinterval counter is set to the number of timer interrupts in thesampling interval (192 timer interrupts) (block 220). Sensor pulses arecounted during this sampling interval.

The system then enables the interrupt (INT) input on the microprocessor30 allowing the wheel sensor interrupt routine to increment the sensorpulse counter (block 222).

A determination is made as to whether a time interrupt has actually beenreceived (i.e. flag set) (block 224). If not, a loop back to block 224provides continuous testing until such time as the flag is set. Once itis set, the interval measuring counter is decremented (block 226) andthe program proceeds to the sub-routine indicated by block 228.

FIG. 19 illustrates a sub-routine beginning with block 228 and includesa determination of when the interval counter reaches zero which means,in practical terms, whether the sampling interval is complete. If not,the program loops back to block 224 as illustrated in FIGS. 18 and 19 byentry block 232. If the sampling period is over, the sensor interruptinput is disabled and the program returns to block 234. In addition,block 234 has the entry point for block 216 from FIG. 20.

In FIG. 20, there is shown the sensor interrupt routine. When enabled, apulse from the wheel sensor causes this routine to be called. In thefirst block (block 236), the pulse counter is incremented and then adecision is made as to whether the sensor pulse is completed. Thisprevents multiple interrupts to be generated from a single pulse (block238). If the pulse is not finished, the system moves back and re-tests.Otherwise, the routine is exited and the system returns to block 240.

FIG. 21 illustrates a sub-routine for the timer interrupt. The internaltimer causes an interrupt to occur every 350 microseconds. Thisinterrupt routine gets the pulse train data from a table and sends it tothe audio output. The pulse train which corresponds to the engine speedis calculated by the main routine. The system begins by decrementing thefiring period counter (block 242).

Then the decision is made to determine whether the period counter isequal to zero (block 244). This is to determine whether the end of thecurrent pulse train has been encountered. If not, the program jumps to anew location (to be explained hereinafter) and is illustrated bytransition block 246. On the other hand, if the counter does equal zero,this is an indication that the pulse train is finished and that datatable pointer is reset to the initial position (block 248).

The new period count calculated by the main routine that starts at block118 is then loaded into the firing period counter and a burst counter isinitialized to its longest period 40 (block 250).

The system generates a random 16 bit number (block 252) and the programproceeds to the sub-routine indicated on FIG. 22 via transistion block254.

The sub-routine continues on FIG. 22. A short delay is addedcorresponding to the random 16 bit number before starting the new pulsetrain (block 256). This delay causes the effect of a slight enginejitter or unevenness which eliminates and unnatural periodicity which isheard as a hum or buzz at the firing frequency.

A random number is also used to generate a misfire as explained above inconnection with FIG. 6. The lower byte of the random number generatedabove (block 254) is ANDed to the "misfire mask" from a look-up table(block 258), and the result is tested to determine if it is equal tozero (block 260).

If it is equal to zero, a misfire is generated by shortening the lengthof the pulse train burst from 40 to 10. Thereafter, the burst count isdecremented (block 264). This is also the entry point for transistionblock 246 from FIG. 21. The system then continues on FIG. 23 by atransistion block 266.

If the burst count equals zero after decrementation (block 268), thenthe burst is done and no more data will be output during the currentpulse train period. In such case, the pulse train data is then sent tothe audio output (block 270). Otherwise, a reset is sent to the timer tocause the next interrupt in 350 microseconds and the timer interruptflag for the sensor pulse counting routine is also set and the programreturns to calculating firing period, etc.

FIG. 24 details the start routine which generates a sound whichsimulates a "kick" start typical of motorcycles. First, a period of 10seconds is loaded into the timeout counter (block 274). This is also theentry point for block 276 detailed hereinafter.

The counter is then decremented (block 276). If the starter button hasbeen depressed (block 278) the program reverts to sub-routine indicatedby transistion block 280. If not, a determination is made if the timeoutis now down to zero (block 282). If not, the program loops back to block276. Otherwise, the program generates a power on warning "beep". Thepurpose of this beep is to send a warning to the operator that the powerof the system has been left on so as not to run down the batteries ifthere is no intention to start the simulator (block 284). The programthen reverts back to block 276 and the cycle resumes.

FIG. 25 begins sub-routine from transistion block 280 in FIG. 24. Adetermination is made if the time on counter has an odd number. An oddnumber is used to determine a successful start while an even number isused to generate a failure to start. In the case of an odd number, theprogram continues via block 286.

If it is an even number, incrementation of the "failed start" counter ismade (block 288). If this is the third failed start (block 290), theprogram jumps to the sub-routine indicated by block 286, otherwise,sounds are generated corresponding to a failed start (i.e. low firingrate that gradually becomes lower, stopping completely after about ahalf second). These values are stored in a look-up table (block 292).

The program then reverts back to block 276 which is the beginning of thestart routine shown in FIG. 25.

Block 286 from FIG. 25 (in the case of a proper start) starts theinterrupt timer and draws from memory a pulse train which produces anaudible sound of a short revving period followed by idling (block 294).

The program then returns to block 296.

FIG. 27 illustrates the object code in Intel standard hex format for apreferred embodiment of the present invention. This object code containssub-routines as generally described herein which could be likewisegenerated by a person skilled in this art based on the above flow-chartsand using a proper compiling device.

It can be appreciated that the above detailed description describes anaudio simulator for a non-motorized vehicle which is capable ofrealistically simulating most of the characteristic sounds and functionsof a motorcycle in this case. It should be likewise appreciated that thebasic sub-routines detailed herein can be adapted to simulate relatedvehicles without departing from the spirit of the invention.

Numerous characteristics and advantages of the invention have been setforth in the foregoing description together with details of thestructure and function of the invention. The novel features thereof arepointed out in the appended claims. The disclosure however isillustrative only, and changes may be made in detail within theprinciple of the invention to the full extent intended by the broadgeneral meaning of the terms in which the appended claims are expressed.

What is claimed is:
 1. A motorcycle simulator for use on a non-motorizedvehicle, comprising:(a) means for producing an electrical signalproportional to the velocity of the non-motorized vehicle; (b) means fordetermining the acceleration of the vehicle from said signal; (c) meansfor producing an audio output corresponding generally to the sound of amotorcycle at the particular velocities; (d) means for providingstep-wise continuous changes in said audio output frequency, saidchanges occurring at particular velocities and accelerations andproducing an audio characteristic corresponding to shifting of gears ona motorcycle; and (e) a starting sequence which randomly determineswhether attempted starting of the simulator will produce an audio outputcorresponding to a rising frequency and then back to an idle frequencycorresponding to a start condition or alternatively an increasingfrequency followed by a decreasing frequency to zero corresponding to anon-start condition.
 2. A simulator according to claim 1 wherein saidparticular velocities are changeable in response to the rate ofacceleration detected during each period of increasing frequency andwherein the velocity where a gear shift output is produced is reducedfor greater rates of acceleration so that rapid acceleration of thevehicle results in earlier gear shifting.
 3. A simulator according toclaim 1 including a starting sequence which randomly determines whetherattempted starting of the simulator will produce an audio outputcorresponding to a rising frequency and then back to an idle frequencycorresponding to a start condition or alternatively an increasingfrequency followed by a decreasing frequency to zero corresponding to ano-start condition.
 4. A simulator according to claim 2 including meansfor detecting a deceleration to zero velocity and maintaining the audiooutput at a frequency corresponding to an idle sound of a motorcycle. 5.A simulator according to claim 2 including means for intermittentlyaltering the audio output to produce a sound corresponding to a misfireof a motorcycle said misfire sound being generated randomly with aprobability which increases with decreasing audio frequency.
 6. Asimulator according to claim 5 wherein a mask byte is ANDed with saidrandom number on a bit by bit basis to produce a numbered result and amisfire is produced if said result equals a predetermined number, saidmask byte being selected in relative to the current frequency of theaudio output and wherein said selected mask byte has a higherprobability of producing a misfire at lower audio frequencies.
 7. Asimulator accordinq to claim 1 wherein said audio output includes afiring period which has an audible pulse train burst component and asilent component and wherein higher audio frequencies are produced byshortening the silent portion.
 8. A simulator according to claim 7including a silent delay period of random length being inserted betweeneach firing period, so that unnatural periodicity sounds will not begenerated.
 9. A motorcycle sound simulator for use in a non-motorizedvehicle, comprising:(a) a sensor attached to said vehicle to detectrotation of a wheel and generate an electrical signal corresponding tothe velocity of the vehicle; (b) means for generating an audio outputwhich includes a firing period having an audible component of a seriesof pulses forming a pulse trail burst, and a silent period and whereinan audio output of varying pitch is produced by shortening the silentperiod; (c) means for step-wise increasing or decreasing the audiooutput frequency at predetermined vehicle velocities to simulate gearshifting sounds; (d) means for determining the acceleration of thevehicle in real time and altering the predetermined step-wise increasesand decreases such that an increased acceleration rate results instep-wise increases at lower velocities and increased deceleration rateresults in step-wise decreases at higher velocities; (e) means forintermittently producing a misfire sound effect at random intervals andinserting the effect in between firing periods, said effect beingproduced by generating a second first period having a silent periodsubstantially longer than said pulse train burst, said effect beingrandomly inserted with a probability decreasing with increasing audiofrequency; and (f) means for randomly producing a no-start effect whenpower is applied to the system, said effect including a rising audiofrequency followed by a falling frequency to zero.
 10. A simulatoraccording to claim 9 including means for inserting a short silent delayperiod of random length between each firing period so that unnaturalperiodicities are reduced.